for Twenty Years in succession on the same Land. 323 
salts. The two Plots, 4 A and 4 A A, have received the same 
description and amount of mineral manure every year from the 
commencement. In addition, 4 A has received 200 lbs. of 
ammonia-salts per acre every year, but 4 AA 400 lbs., or double 
the amount the first 6 years, and only 200 lbs., or the same as 
4 A, the next 10 years. Any increase, therefore, on Plot 4 AA 
over 4 A, during the 10 years in which they both received the 
same amount of ammonia-salts, may presumably be attributed to 
the extra amount applied to 4 AA during the first 6 years. 
For the sake of more exact comparison than the record of the 
actual quantities of dressed corn would afford, the total corn 
per acre has, in each case, been calculated into bushels of 
521bs. 
It appears that, during the 10 years, there was an excess of 
produce on 4 AA compared with 4 A, due to the unexhausted 
residue from the previous nitrogenous manuring, of nearly 
28 bushels of corn, and just 28 cwts. of straw ; or an annual 
average of 2J bushels of corn, and 2J cwts. of straw. It is also 
to be observed that the excess in the tenth year was almost exactly 
the same as the average of the 10 years, showing that the residue 
was not even then exhausted. There was, then, in this case, a 
marked effect upon the succeeding barley crops, from the extra 
ammonia-salts applied in the first 6 years. 
Table XLI. shows, in like manner, the effects on succeeding 
barley-crops of a previous extra supply of nitrogen in the form of 
nitrate of soda. The two Plots, 1 N and 2 N, each received in 
the first year, 1852, 3^ cwts. superphosphate of lime, and 
300 lbs. sulphate of potass per acre. Each year since, 1 N has 
received 275 lbs. nitrate of soda, and 2 N 550 lbs. during the 
first 5 years, but subsequently only 275 lbs., or the same 
amount as 1 N. 
The Table shows that, during the 14 years after the cessa- 
tion of the extra application of nitrate on Plot 2 N, it continued to 
give more produce than 1 N, amounting in the 14 years to 
about 51^ bushels of corn, and rather over 30 cwts. of straw, or 
to an average per acre per annum of 3^ bushels of corn, and 
2^ cwts. of straw. Here, again, as in the experiments with the 
ammonia-salts, the increase in the last year of the series is almost 
precisely the same as the average increase over the whole period. 
The differences from year to year are obviously due to pecu- 
liarities of season. The result is clear, however, that with the 
nitrate, as with the ammonia-salts, there was a somewhat lasting 
effect from the extra amount applied during the earlier years. 
It will be of much interest to compare the above results with 
barley, with those obtained with wheat ; and it is especially 
desirable to adduce those which bear upon the point relating to 
VOL. IX. — S. S. z 
